A number of attempts have been made to automate the treatment of phobics through self-administered variants of systematic desensitization. However, previous research has largely consisted of case reports or insufficiently controlled studies relying on self- reported measures of fear change. The present study will evaluate the clinical effectiveness of a manual for self-administered desensitization using a group design with appropriate experimental controls. Self-referred Ss who are screened for fear of snakes will be randomly assigned to either one of three treatment groups, a placebo- attention control, or a no-treatment wait list control. Treatment groups will receive (a) desensitization administered by a therapist in a clinic setting, (b) desensitization self-administered by the client in a clinic setting or (c) desensitization self-administered by the client at home. Pre- and post-treatment fear assessments will include behavioral, self-report and physiological measures of fear change. If a manual for self-administered desensitization is clinically effective than a significant step towards the goal of self-control in the management of behavioral problems will have been made. It is critical, however, that this issue be adequately evaluated since psychologists have already begun to recommend self-help programs.